Particulate tin power and manufacturing method thereof

ABSTRACT

The present invention relates to particulate tin powder and a manufacturing method thereof. More particularly, the present invention relates to a method of manufacturing particulate tin powder including i) preparing tin salt solution, ii) adding chelating agents to the tin salt solution, iii) adjusting pH of the tin salt solution to which the chelating agents are added, and iv) reductively depositing tin powder by adding reductant to the tin salt solution.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2009-0085899 filed with the Korea Intellectual Property Office onSep. 11, 2009, the disclosure of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to particulate tin powder and amanufacturing method thereof. More particularly, the present inventionrelates to a method of manufacturing particulate tin powder thatextracts the particulate tin powder by adding reductant to tin-saltadding complexing agents and particulate in powder manufactured thereby.

2. Description of the Related Art

World countries are commonly recognize the seriousness which wastes ofelectronic products that rapidly increase with development of anelectronics industry give to an environment and legal regulation fortoxic elements is in progress. It is not too much to say that securing aclean technology in a mounting technology part based on a semiconductorand the electronics industry is connected directly with survival of ourindustries, in a series of international regulation movements.

In particular, solder powder is widely used as configuration powder of aconductive adhesive used for via-hole charging on a multilayer printedwiring board or at the time of mounting IC components, etc. on a printedwiring board. As known soldering, eutectic soldering of tin of 63 w %and plumbum of 37 w % has been primarily used.

However, plumber which is contained in components of home appliancesrepresented as a Braun tube of a television and other electronicapparatuses is a cause of environmental pollution including causingwater pollution, etc., such that a so-called lead-free solderingmaterial is generally used in mounting in order to reduce the totalamount of plumber contained in the home appliance.

That is, although a Sn—Pb soldering component has been primarily used inthe related art, a usage cost or a waste cost of a solder containingplumbum is increased day by day due to groundwater contaminationgenerated by eluting plumbum components when the plumbum components arewasted and buried, restriction or prevention in using plumbum in adeveloped country, plumbum using company's economical sanction or taximposing as an environmental concern is increased worldwide as describedabove, such as at the present, the lead-free soldering material isprimarily used.

Soldering powder, etc. is configured by metallic particulate powder anda method for preparing the metallic particulate powder includes amechanical grinding method, an atomization process, a gas phasereduction method, a gas evaporation method, etc., but the atomizationprocess is generally used to prepare the soldering powder or tin powderconfiguring the soldering powder.

The atomization process prepares the tin powder by atomizing solutioncontaining metal such as tin, etc., using the atomization solution asindividual droplets, and cooling the droplet, a solder powder formingdevice (FIG. 1) using the atomization process includes a metal meltingunit 10 melting tin (Sn) metal having a lump form, a powder forming unit20 forming soldering melting metal (hereinafter, referred to as “moltenmetal”) discharged from the metal melting unit 10 as solder paste powder(hereinafter, referred to as “powder”), and a collection tank 30collecting solder paste powder, a switch 40 which is a ball valve or athrottle valve for maintaining airtightness by blocking air in thepowder forming unit 20 at the time of exchanging the collection tank 30.The powder forming unit 20 includes an atomizer 23 a high-speed motor 23b that rotates at high speed is fixed to a lower center of a chamber 21by a support 23 c and a rotation disk 23 a crushing and forming themelting metal dropped while being installed on a rotation shaft of thehigh-speed motor 23 b by using centrifugal force as powder.

An operation process will be described in brief by a spraying devicehaving the above-mentioned configuration. First, when the solderingmetal having the lump form is inputted into the chamber 21 under avacuum state and melted, such that the melting metal is formed, theformed melting metal is discharged in a certain amount through a nozzleby using a tundish 22. The discharged melting metal is dropped to therotation disk 23 a that rotates at high speed of approximately 20,000 to35,000 rpm by the high-speed motor 23 b of the atomizer 23 and crushedinto small particles by the centrifugal force to be formed as powder.The powder is cooled by a cooler 24 installed on the outer periphery ofthe chamber 21 and thereafter, is collected in the collection tank 30through the switch 40.

The soldering powder or tin powder acquired in the preparation methodhas an advantage in that dispersibility of separation is excellent bycomparing the soldering powder or tin powder with powder acquired inother preparation methods such as a wet method, but has a disadvantagein that particle size distribution is extremely wide, a limit of theparticle size distribution is generally in the range of 1 um to 10 um,and particulate powder having 5 um or less is difficult to acquire.

Since via-hole leveling of a multilayer print wiring board isdeteriorated and a particle diameter is large at the time of usinglarge-sized powder prepared by the above-mentioned atomization method,sinterbility is deteriorated at low temperature, thereby degradingreliability. Further, in recent years, as a pitch size of the multilayerprint wiring board is also decreased to 50 um or less due to a decreasein weight and size of electronic apparatuses, problems caused at thetime of using the large-sized powder will rise more severely.

Further, although a method for preparing the soldering metal powder suchas tin, etc. using the existing wet method includes a method using asubstitution wet method or a method for preparing colloidal solutioncontaining tin power by reducing tin components from organic solvent,these methods have a disadvantage in that an additional separationprocess is required, such that a process is complicated and amanufacturing cost is high to acquire a large amount of tin powder andanother advantage in that it is difficult to acquire tin powderparticulates having high purity while having a means particle size of 1μm or less and narrow particle distribution.

As a result, the inventor has invented particulate tin power havingnarrow particle size distribution and high purity, which is aparticulate having reliability enough to for a minute circuit or chargea via-hole having a minute diameter as well as the process is simple andeconomical without requiring an additional separation process orsubstitution process and a manufacturing method thereof.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provideparticulate tin powder which has a simple manufacturing process and iseconomical, and a manufacturing method thereof without requiring anadditional separation process or substitution process.

It is, therefore, another object of the present invention to provideparticulate tin powder having narrow particle size distribution and highpurity, which is a particulate having reliability enough to form aminute circuit and fill a via-hole having a minute diameter, and amanufacturing method thereof.

In order to achieve the above-mentioned object, in accordance with oneaspect of the present invention, there is a method of manufacturingparticulate tin powder including i) preparing tin salt solution, ii)adding chelating agents to the tin salt solution, iii) adjusting pH ofthe tin salt solution to which the chelating agents are added, and iv)reductively depositing tin powder by adding reductant to the tin saltsolution.

Further, the present invention provides the method of manufacturingparticulate tin powder wherein the concentration of the tin saltsolution is 0.01 to 5 mol/L and the tin salt solution is composed ofSnCl₂, SnSO₄, SnI₂, SnF₂ SnBr₂, Na₂SnO₃, or SnCH₃SO₃ solution.

Further, the present invention provides the method of manufacturingparticulate tin powder wherein the concentration of the chelating agentsis 0.05 to 15 mol/L and the chelating agents are composed of nitrogen(N) or oxygen (O) containing compound or the chelating agents arecomposed of thiourea or thiourea derivatives.

In addition, the present invention provides the method of manufacturingparticulate tin powder wherein the reductant is composed of boron (B),phosphorus (P), or nitrogen (N) containing compound or the reductant iscomposed of sulfide, disulfide, or thiol.

In order to achieve the above-mentioned object, in accordance withanother aspect of the present invention, there is particulate tin powdermanufactured by a manufacturing method including i) preparing tin saltsolution, ii) adding chelating agents to the tin salt solution, iii)adjusting pH of the tin salt solution to which the chelating agents areadded, and iv) reductively depositing tin powder by adding reductant tothe tin salt solution.

Further, the present invention provides the particulate tin powderwherein the purity of the tin powder is equal to or larger than 95%, amean particle size (Dv50) of the tin powder is equal to or smaller than1 μm, and the particle size distribution of the tin powder is 0.1 to 5μm.

In accordance with an embodiment of the present invention, through amethod of manufacturing particulate tin powder can be acquiredparticulate tin powder having narrow particle size distribution and highpurity, which is a particulate having reliability enough to form aminute circuit and fill a via-hole having a minute diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the present generalinventive concept will become apparent and more readily appreciated fromthe following description of the embodiments, taken in conjunction withthe accompanying drawings of which:

FIG. 1 is a partial cut perspective view of an apparatus for preparingsolder paste powder by a centrifugal atomization process;

FIG. 2 is an SEM photograph of particulate tin powder in accordance witha manufacturing method of the present invention;

FIG. 3 is a graph showing an EPMA qualitative analysis result ofparticulate tin powder in accordance with a manufacturing method of thepresent invention; and

FIG. 4 is a graph showing a thermal analysis (DSC) melting pointanalysis result of particulate tin powder in accordance with amanufacturing method of the present invention.

DETAILED DESCRIPTION OF THE PREFERABLE EMBODIMENTS

Particulate tin powder and a manufacturing method thereof in accordancewith the present invention will be now described in detail withreference to the accompanying drawings.

FIG. 1 is a partial cut perspective view of an apparatus for preparingsolder paste powder by a centrifugal atomization process, FIG. 2 is anSEM photograph of particulate tin powder in accordance with amanufacturing method of the present invention, FIG. 3 is a graph showingan EPMA qualitative analysis result of particulate tin powder inaccordance with a manufacturing method of the present invention, andFIG. 4 is a graph showing a thermal analysis (DSC) melting pointanalysis result of particulate tin powder in accordance with amanufacturing method of the present invention.

A method of manufacturing particulate tin powder in accordance with thepresent invention includes i) preparing tin salt solution, ii) addingchelating agents to the tin salt solution, iii) adjusting pH of the tinsalt solution to which the chelating agents are added, and iv)reductively depositing tin powder by adding reductant to the tin saltsolution.

At the first step, tin salt solution may be all kinds of tin saltsolution which is commercially usable such as SnCl₂, SnSO₄, SnI₂, SnF₂SnBr₂, Na₂SnO₃, or SnCH₃SO₃ and the concentration of tin salt solutionis preferably 0.01 to 5 mol/L in order to reductively depositparticulate tin powder having high purity.

Meanwhile, at the second step, chelating agents for forming tin ions intin salt solution manufactured at the first step and chelates are added.The chelating agents may use all kinds of tin salt solution which iscommercially usable such as triethanolamine (TEA), tartrate, cyanide,malonate, citrate, nitrilotriacetate, pyrocatecol, EDTA, etc.Preferably, chelating agents may be used which are composed of nitrogen(N) or oxygen (O) containing compound providing unshared electron pairsor thiourea or thiourea derivative.

Further, depending on the kind and density of the used tin saltsolution, chelating agents of an appropriate amount may be added andpreferably, chelating agents having a density 0.05 to 15 mol/L may beadded.

At the third step, in order to reductively depositing tin ions formingchelates with the added chelating agents, the tin salt solution shouldbe adjusted with appropriate pH by adding acid or base such as NaOH orHCl so that reductant reacts.

At the fourth step, tin powder is finally deposited without anadditional separation process by adding the reductant to tin saltsolution adjusted with appropriate pH where the reductant can operate.The reductant may adopt all kinds of tin salt solution which can becommercially used such as formaldehyde (HCHO), hypophsphites (H₂PO₂),hytrazine (N₂H₄), dimethylamine borane (DMAB), sodium boron hydride(NaBH₄), SPS (bis-3 sulfopropyl disulfide), etc. Preferably, thereductant may be composed of boron (B), phosphorus (P), or nitrogen (N)containing compound or may be composed of sulfide, disulfide, or thiol.

At this time, reaction temperature can be adjusted for each reducingagent at room temperature to 80° C.

The particulate tin powder finally manufactured by the manufacturingmethod i) preparing tin salt solution, ii) adding chelating agents tothe tin salt solution, iii) adjusting pH of the tin salt solution towhich the chelating agents are added, and iv) reductively depositing tinpowder by adding reductant to the tin salt solution has high purity of95% or higher.

Further, the reductively deposited tin powder has a sphericalparticulate shape and narrow particle size distribution and preferably,a particulate shape having a mean particle size (Dv50) of 1 μm or lessand narrow particle size distribution of 0.1 to 5 μm.

Hereinafter, an embodiment of a method for manufacturing particulate tinpowder in accordance with the present invention will be described.

Embodiment

After tin(II) methane sulfonate solution of 0.35 mol/L is manufacturedand agitated, thiourea of 1 mol/L is added and agitated. Tin saltsolution to which thiourea is added is adjusted to pH of 1 to 2 by usingHCL and thereafter, agitated. Tin is finally reductively deposited byslowly adding NaS2O4 (sodium dithionite) which is disulfide of 0.03mol/L to tin salt solution of which pH is adjusted.

As a result of analyzing particle sizes of particulates of finallydeposited particulate tin powder by using the MSS instrument of MalvernInstruments Ltd. as shown in FIG. 2, a mean particle size (Dv50) is 0.58um and particle size distribution is in the range of 0.1 um to 5 um.Further, it is verified that particulate tin powder deposited throughSEM is a spherical particulate tin particle.

In addition, it is verified that the deposited particulate tin powder iscomposed of Sn and O through the EPMA analysis result of FIG. 3(however, C is an analysis pre-processing coating and carbon tapecomponent) and as a result of thermal analysis (DSC) for verifying puretin particles (mp. 210° C.) or tin oxide particles (mp. 1080° C.), it isverified that the deposited particulate tin powder is pure tin particleshaving a melting point of approximately 214° C.

By applying the method of manufacturing the particulate tin powder usingthe reduction wet method in accordance with the present invention, it ispossible to manufacture pure particulate tin powder having a meanparticle size of approximately 0.5 um which could not be acquired by theknown method (atomization method).

Accordingly, it is possible to acquire the particulate tin powder havingnarrow particle size distribution and high purity by improving via-holeleveling of a multilayer print wiring board and improving sinterbilityat low temperature by atomizing the particle diameter to solve a problemin that reliability is deteriorated through the method of manufacturingthe particulate tin powder.

As described above, although the preferable embodiments of the presentinvention have been shown and described, it will be appreciated by thoseskilled in the art that substitutions, modifications and changes may bemade in these embodiments without departing from the principles andspirit of the general inventive concept, the scope of which is definedin the appended claims and their equivalents.

1. A method of manufacturing particulate tin powder, comprising: i)preparing tin salt solution; ii) adding chelating agents to the tin saltsolution; iii) adjusting pH of the tin salt solution to which thechelating agents are added; and iv) reductively depositing tin powder byadding reductant to the tin salt solution.
 2. The method ofmanufacturing particulate tin powder of claim 1, wherein theconcentration of the tin salt solution is 0.01 to 5 mol/L.
 3. The methodof manufacturing particulate tin powder of claim 1, wherein the tin saltsolution is composed of SnCl₂, SnSO₄, SnI₂, SnF₂ SnBr₂, Na₂SnO₃, orSnCH₃SO₃ solution.
 4. The method of manufacturing particulate tin powderof claim 1, wherein the concentration of the chelating agents is 0.05 to15 mol/L.
 5. The method of manufacturing particulate tin powder of claim1, wherein the chelating agents are composed of nitrogen (N) or oxygen(O) containing compound.
 6. The method of manufacturing particulate tinpowder of claim 1, wherein the chelating agents are composed of thioureaor thiourea derivatives.
 7. The method of manufacturing particulate tinpowder of claim 1, wherein the reductant is composed of boron (B),phosphorus (P), or nitrogen (N) containing compound.
 8. The method ofmanufacturing particulate tin powder of claim 1, wherein the reductantis composed of sulfide, disulfide, or thiol.
 9. Particulate tin powermanufactured by reductive deposition in a manufacturing method disclosedin claims 1 to
 8. 10. The particulate tin powder of claim 9, wherein thepurity of the tin powder is equal to or larger than 95%.
 11. Theparticulate tin powder of claim 9, wherein a mean particle size (Dv50)of the tin powder is equal to or smaller than 1 μm.
 12. The particulatetin powder of claim 9, wherein the particle size distribution of the tinpowder is 0.1 to 5 μm.